[mutter] (15 commits) ...wayland: Implement on-demand start of Xwayland

[Carlos Garnacho <carlosg src gnome org>]

Summary of changes:

  79b5ece... core: Ensure passive key grabs are only set up on X11 (*)
  9109fa0... x11: Add meta_x11_get_display_name() function (*)
  ca51cd8... core: Prepare MetaStackTracker for X11 display being closed (*)
  d3d1ff1... x11: Do not queue stack operation for guard window (*)
  500a692... core: Manage only X11 windows when (re)starting (*)
  8b62f48... wayland: Rename xwayland init/shutdown functions (*)
  9a10b8f... wayland: Disconnect signal when the display closes (*)
  319f7f5... compositor: Add explicit API call to redirect X11 windows (*)
  f5a2694... wayland: Add tracking of X11 windows (*)
  e894929... wayland: Refactor code setting up the display socket (*)
  7ef32f7... wayland: Add setting/api to check the policy to set up the  (*)
  123b401... x11: Shuffle x11-stack destruction in MetaX11Display dispos (*)
  879f5f0... x11: Add "closing" flag to MetaX11Display (*)
  0c5866a... core: Avoid queueing a stack operation on the frame when th (*)
  141373f... wayland: Implement on-demand start of Xwayland (*)

(*) This commit already existed in another branch; no separate mail sent